Some of the conventional internal combustion engines are provided with a cam-chain dropout preventing member in addition to a cam chain tensioner for control of behaviors, such as vibrations, of a cam chain which transfers power from a crankshaft to a camshaft. The cam-chain dropout preventing member prevents the cam chain from dropping out and falling in the internal combustion engine during maintenance work or the like of the engine.
An object of the invention is to reduce load on the cam chain tensioner and to further improve durability of a tensioner lifter by imparting a cam chain guiding function to control the behaviors of the cam chain to the cam-chain dropout preventing member to prevent such a dropout of the cam chain.